Paint binders are disclosed in DE-OS No. 23 20 301, corresponding to Canadian Pat. No. 1,021,493, which are obtained by reaction of MANNICH-bases (of condensed phenols, secondary alkanolamines and formaldehyde) with an epoxy resin. Similar binders are disclosed in DE-OS No. 24 19 179, corresponding to U.S. Pat. No. 3,994,989. As stated in DE-OS No. 27 11 385, such systems have the disadvantage that amines are split-off on stoving. Therefore, it has been proposed to use a MANNICH-condensation product of a phenol and/or an alkylphenol, a primary amine, and formaldehyde.
Another proposal for improving the products of the DE-OS No. 23 20 301 and DE-OS No. 24 19 179 references is disclosed in DE-OS No. 27 11 425, corresponding to U.S. Pat. No. 4,134,932, where to such binders water-insoluble urethane group carrying resins are added, and in particular the modified polyamide amine resins. To avoid the splitting off of amines, DE-OS No. 25 41 801, corresponding to U.S. Pat. No. 4,086,292, proposes to react the MANNICH-base with an epoxy resin based on polyhydric alcohols, the hydroxy groups of which are reacted with semi-blocked diisocyanates and optionally with a urethane-free epoxy resin. DE-OS No. 25 54 080, corresponding to Canadian Pat. No. 1,074,489, describes a similar process. In all these cases the reaction with the isocyanates is to suppress the split-off of amines on stoving.
The products produced according to the teachings of the aforesaid references, however, do not meet the requirements of the automobile industry with respect to corrosion resistance at crosslinking temperatures of from about 150.degree. to 170.degree. C. and the adhesion of the stoved film, particularly the adhesion of subsequent coats.
Our copending application filed concurrently with this application entitled "Self-Crosslinking Cationic Paint Binders Containing Urea Groups and Process of Manufacture" discloses cationic binders and a process for producing self-crosslinking cationic binders water-dilutahle on protonation, based on reaction products of substituted urea-phenol-formaldehyde condensates and epoxy resins, and to the binders thereby produced. The process and binders are characterized in that
(A-1) an aminoalkylation product carrying an average of at least one NH-group per molecule, of phenol and/or a substituted phenol, preferably a monoalkyl-, monoaryl- or monoaralkylphenol with one or optionally two phenolic hydroxy groups, a primary alkylamine and/or primary alkanolamine and/or alkylenediamine and formalydehyde or a formaldehyde donating compound is reacted with a semi-blocked diisocyanate, or PA1 (A-2) a semi-blocked diisocyanate is reacted with a primary alkylamine and/or primary alkanolamine and/or alkylene diamine and the resulting substituted urea is reacted with formaldehyde or a formaldehyde donating substance and phenol and/or a substituted phenol ptreferably a monoalkyl-, monoaryl-, or monoaralkylphenol with one or optionally with two phenolic hydroxy groups, PA1 (B) 50 to 100% of the phenolic hydroxy groups of component (A) are reacted with epoxy compounds, preferably with diepoxy resins with an epoxy equivalent weight of between 50 and 2000. PA1 (A-1) an aminoalkylation product carrying an average of at least one NH-group per molecule, of phenol and/or a substituted phenol, preferably a monoalkyl-, monoaryl-, or monoaralkylphenol with one or optionally two phenolic hydroxy groups, a primary alkylamine and/or primary alkanolamine and/or alkylene diamine and formaldehyde or a formaldehyde donating substance is reacted with a semi-blocked diisocyanate or PA1 (A-2) a semi-blocked diisocyanate is reacted with a primary alkylamine and/or primary alkanolamine and/or alkylene diamine and the resulting substituted urea is reacted with formaldehyde or a formaldehyde donating substance and phenol and/or a substituted phenol, preferably a monoalkyl-, or monoaryl-, or monoaralkylphenol with one or optionally two phenolic hydroxy groups, PA1 (B) 50 to 100% of the phenolic hydroxy groups of component (A) are reacted with monoepoxy compounds and, subsequently, PA1 (C) 50 to 100 mole-% of the aliphatic hydroxy groups set free through the reaction with the monoepoxy compound are reacted with equivalent quantities of a polyisocyanate.
and in a further reaction step
These materials meet the requirements of the automobile industry both with respect to corrosion and adhesion.